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20121108
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. and in that environment, you have then the ejection of alpha, beta and gamma particles. so it's almost simple geometry. right now, this particle we'd call an alpha particle. this is a helium nucleus. and i'll write that helium nucleus like this. and i'll put a two down here and a four here. and this nomenclature, i hope you're familiar with. this is simply the atomic number. it tells you it's atomic number two in the periodic table of substances, yeah? it's got two positive charges. and the four refers to the atomic mass unit. and that's the number of nucleons altogether. i call this, by the way, nucleons. i can call you a people, a person, but a person can be a male or female. nucleon can be a proton or neutron. see what i'm saying? but there's four nucleons altogether, so it has a mass of four and atomic number two. so that would be the configuration. if i put another proton in there, then it would now be-- does anyone know? it would be the element lithium because now it would have three and up here would be five. and any nucleus that has three protons, by definition and by chemical properties, will
into an environment of heavy balls or light balls? heavy balls. and you want the thing to slow down. let me ask you this. if i take a ball and i throw it against a brick wall-- [makes sounds] --when it bounces off, will it bounce off a lot slower or about the same? about the same. about the same. if i take a golf ball and i throw it against a bowling ball, is that bowling ball gonna slow the golf ball down? no, it's not. so what you do is you take the golf ball and you throw into an arena of ping-pong balls. and if you do that, it will give what? give the energy to ping-pong ball and it itself will slow down. and so what do you do is you take these things and you bounce them off atoms like the size of carbon. did you ever hear about the heavy water? you bounce them off light atoms or molecules and these things will slow down, so they're moderated and will cause the reaction of more of this fission. you call--nuclear fission, gang, breaking apart, nuclear fission, and you will fission more atoms. anyway, this is something that cause an awful lot of excitement. because along with these two, it turns
effective agricultural environment around fez within, say, 15 or 20 miles radius. but you also had very effective forms of nonhuman transport -- donkeys, camels, horses, mules -- that could bring in all of the kinds of supplies that the city needed. now, that's one reason why you had such high population densities. one of the effects of really high population densities, of course, is to create very dense urban markets, lots of consumers concentrated in small spaces. and this is one of the reasons why fez has such a high degree of urban specialization. keach: as in ancient ostia, almost everyone in fez is a full-time specialist. in the tanning industry alone, there are some 20 specialized activities required to process skins into leather. there are washers and hair removers, buyers and sellers, and transport specialists. there are even specialties within a specialty. there are people who handle the donkeys that bring skins into the market, while others handle the donkeys taking skins out. this is a hair removing factory. it is run by mr. abdelrrahman ovadghiri. interpreter: we get up ear
on the environment. president obama renewed his commitment to "freeing ourselves from foreign oil" in his reelection victory speech last week. energy department data shows u.s. imports of crude had fallen 11% this year and the country is on track to produce the most oil since 1991. the syrian military continues to launch attacks on the border town, sending hundreds of civilians fleeing to neighboring turkey. the new bombings come days after more than 11,000 syrian civilians were forced out during strikes last week, one of the largest refugee flights of this year in conflict to date. speaking in geneva, the head of disaster in crisis management at the international federation of red cross and red crescent societies warned turkey needs major aid to handle the growing number of syrian refugees. >> we have seen a doubling of the camp population since july 2012, and i think as you have seen over the last few days, there has been an increase in the number of syrians moving into turkey. they now recognize the situation is becoming prolonged. the initial thoughts the population might be displaced for shorte
substances, or carcinogens. harold varmus: obviously, environment also contributes to function and disease but knowing what genes are inherited by any organism is essential to a full understanding of how they operate and how they misfunction when disease occurs. only five to ten percent of all cancers are thought to be inherited. for instance, women with mothers or sisters who have breast cancer are at increased risk for developing the disease. i'd get it very early, and be very treatable... i wasn't surprised because both my mother and my grandmother had-- my maternal grandmother, had had the same kind of late onset. and i had helped them both through their bouts with it. and so i knew when i saw the irregularity in my breast line what it was, and just moved forward from there. the ucla breast center, a unit of the jonsson cancer center, specializes in treating and counseling women at high risk for breast cancer. experts from a variety of fields work with patients. a nurse practitioner takes the patient's history... a nutritionist with a special interest in breast cancer talks about the r
Search Results 0 to 4 of about 5